Derivatization-Enabled Detection of Formalin From Preserved Tissues Using Coated Blade Spray Mass Spectrometry

Formalin-fixed, fluid-preserved specimens in natural history collections offer invaluable scientific and cultural insight but pose genomic challenges due to molecular degradation and persistent chemical hazards. In particular, residual formaldehyde can impair downstream molecular workflows and present occupational safety risks for collection handlers. Formaldehyde modifies biological macromolecules by forming covalent crosslinks between nucleic acids and proteins and also by promoting DNA fragmentation, which lowers extraction efficiency and limits the recovery of amplifiable genetic material. To address the need for minimally invasive, rapid formaldehyde detection, we developed a coated blade spray mass spectrometry (CBS-MS) workflow using on-blade derivatization with 2,4 dinitrophenylhydrazine (2,4-DNPH). A custom 3D-printed multiblade holder enabled rapid sequential analysis of 12 blades held in identical positions. Qualitative confirmation on formalin-fixed mammals established detection, while application to archival specimens of the minute fruit bat (Cynopterus minutus) detected formaldehyde in samples recorded only as alcohol-preserved. Variation in signal intensity was observed across replicates, and paraformaldehyde was visually apparent. Overall, the CBS-MS approach offers a minimally invasive, efficient strategy for characterizing preservation chemistry in fluid-stored specimens.